This application is a national stage of PCT/EP00/03974 filed 2 May 2000 and is based upon German national application 199 24 838.9 of 29 May 1999 under the International Convention.
The invention relates to an apparatus for spinning liquid polymers to produce polymer filaments, whereby the liquid polymer flows through a polymer duct with a first heating jacket to a spinning pump with a second heating jacket, which displaces the polymer through a plurality of conduits to spinning packets and extrudes the polymer through the spinneret downwardly to form filaments, whereby the conduits downstream of the spinning pump, the spinning packets and the spinneret are located in at least one spinning housing that is traversed by heating fluid. The invention also relates to a method of heating the spinning apparatus.
Spinning apparatuses with heating of this type are known from DE 196 24 946 A1 and DE 198 09 495 A1. The different. heated parts of the apparatus are maintained, in this case, approximately at the same temperature level which is prescribed by the heating fluid used.
The invention has as its object to maintain the molten polymer upstream of the spinning housing, independently of the temperature in the spinning housing, at the lowest possible temperature so as to exclude possible damage to the polymer.
According to the invention the object is attained in the spinning apparatus described at the outset in that between the spinning housing traversed by the heating fluid on the one hand and on the other hand the first and second heating jackets and the spinning pump, there is a spacing of at least 5 mm and preferably at least 10 mm. This spacing ensures a thermal decoupling and ensures that the polymer will be held at the lowest possible temperature as long as it has still not entered the heated spinning housing. In this manner deterioration in the flowing polymer, which can arise as a result of relatively high temperatures, can be completely or largely excluded.
In addition to a spatial separation of the heated spinning housing, it is advantageous in accordance with a further feature of the invention to effect the heating of the spinning apparatus in a suitable manner. For this purpose heating fluid in the form of a vapor is conducted from a first supply vessel into the spinning housing and heating fluid from the later is discharged, heating fluid from a second supply vessel is fed through the first and/or second heating jackets, and care is taken such that the temperature of the heating fluid in a vapor state fed to the spinning housing is 10 to 40xc2x0 C. higher than the temperature of the heating fluid that is fed to the first and/or second heating jackets.
The heating fluids can be prepared with different temperatures in two supply vessels. As a heating fluid, for example Diphyl, is suitable and is commercially available in various modifications whereby the same heating fluid or different heating fluids can be prepared in the two supply vessels. To maintain the temperature difference on the one hand in the region of the spinning pump and the polymer feed conduits and on the other hand in the spinning housing, the region between the spinning housing on the one hand and the first and second heating jackets on the other hand can be maintained free from the heating fluid. As a result the desired temperature difference can be maintained during operation.
The supply of heating fluid to the first and second heating jackets can be coupled in many cases; thus it is possible to feed the heating fluid coming from the supply vessel initially through the first heating jacket and then through the second heating jacket or in the reverse order. Usually the first and second heating jackets are heated with liquid heating fluid. It is further possible to operate the first and second heating jackets also with separate heating circulations.
As the polymer one can use for example polyester or polyamide. The liquid polymer usually derives from an extruder for the melting of polymer granules but, however, can be from a polymerization reactor. The polymer is admitted to the region of the spinning pump at a temperature of 270 to 300xc2x0 C. and is extruded through the spinneret with a temperature of about 295 to 320xc2x0 C.